Optical recording medium

ABSTRACT

A recordable optical recording medium comprising a recording layer containing an organic dye which can absorb a laser beam and a metal reflective layer directly or via another layer on a transparent supporting substrate having a pre-groove and a pre-pit, wherein the organic dye has a refractive index nk of 2.2 or more at a reproduction wavelength λ 2 ; in relation to the reproduction wavelength λ 2 , the depths of the pre-groove and the pre-pit on the substrates are more than λ 2 /4; and the following equations are satisfied: 
     
       
         0.25 r≦wg≦ 0.38 r;   
       
     
     
       
         0.25≦ wp/wg ≦0.75; 
       
     
     
       
         θ gr≦θpr ; and 
       
     
     
       
         θ pr≦θpt   
       
     
     wherein r is a recording laser beam diameter represented by λ 1 /NA where λ 1  is a recording wavelength [μm] and NA is a numerical aperture for an object lens; wg [μm] and θgr are a half value width and a cross-section tilting angle in a substrate radial direction for the pre-groove, respectively; and wp [μm], θpr and θpt are a half value width, a cross-section tilting angle in a substrate radial direction and a cross-section tilting angle in a tangential direction for the pre-pit, respectively.

TECHNICAL FIELD

This invention relates to an optical recording medium on whichinformation can be recorded and/or reproduced using a laser beam. Inparticular, it relates to a hybrid type high-density optical recordingmedium which is a recordable recording medium allowing recording with ahigher density than a CD and comprises a pre-pit and a pre-groove on asubstrate.

BACKGROUND ART

Among disk media for optical recording, a recordable compact disk onwhich recording can be performed only once, and has been popularly usedbecause of its compatibility with a common read-only CD-ROM. For adigital versatile disk (DVD) with a higher recording density than a CD,recordable media have been developed, among which a recordable DVDR isexpected to become popular because of its higher compatibility with aDVD-ROM. These recordable media use an organic dye in a recording layer,in which a dye irradiated with a laser beam is locally heated to undergochemical and/or physical change such as decomposition, deformation,vaporization, melting and solidification to form a pit, allowinginformation to be recorded.

Meanwhile, there has been proposed an optical recording medium combininga read-only region such as the above CD-ROM and DVD-ROM (ROM region) anda recording region or recordable region such as the above CDR and DVDR(R region) in a single disk. Such specifications will become veryimportant. Such a disk is referred to as a “hybrid disk”, characterizedin that on a substrate, a pre-pit and a pre-groove are formed in a ROMand a R regions, respectively.

Recently, in consumer applications, there has been steady shift from aCD to DVD. In the process, there has been emphasized importance ofcopyright protection for music, image and moving picture software. Thus,it has become inevitable to thoroughly prevent copying particularly fora DVDR medium permitting recording with the same format. It has been,therefore, standardized to incorporate control data for copy preventionas an ROM region in a data control region on a disk in advance.Specifically, all DVDRs sold in a customer market must be supplied as ahybrid type. There have been needs to propose a convenient and stablehybrid type DVDR as soon as possible.

Although a hybrid disk using an organic dye as a recording film has beenstandardized for CDR, providing a signal amplitude (recording modulationfactor) is more difficult in an ROM region than an R region andtherefore, satisfactory properties have not been achieved. It is becausea recording layer comprising a dye is formed not only on a pre-groove inthe R region but also on a pre-pit in the ROM region so that the samepre-pit shape as that in a commercially available CD does not give anadequate modulation factor.

JP-As 4-146537 and 9-120586 have disclosed that depths of a pre-pit andpre-groove can be adjusted to control a difference in optical pathlengths and thus to achieve good signal balance. This technique may,however, have drawbacks that it generally requires difficult stampercutting of two beams in production, and that a recording signal may bedegraded because a relatively shallower groove has a V shape.

There has been proposed an approach that a deposition position of arecording layer is controlled such that the recording layer is formedonly over an R region while directly forming a reflective layer over anROM region. Boundary control is, however, difficult from an R region toan ROM region or an ROM region to an R region. In particular, it cannotbe a practical solution in the light of compatibility in reproductionwith a CD or DVD player.

A temporary approach has been adopted in most cases, where a pre-pit isformed by in advance conducting recording by a writer in a predeterminedregion in a recordable disk having only a usual R region fordistributing a small number of products. Such an approach cannot be, ofcourse, applied to a mass production.

It is thus desirable for an ROM region in a hybrid disk that the pre-pitinformation is formed from a stamper template by an appropriatetechnique such as injection molding.

DISCLOSURE OF INVENTION

An objective of this invention is to provide a hybrid disk type ofoptical recording medium in which a recording layer comprising at leasta dye and a reflective layer are sequentially formed on a substrateincluding an ROM region having a pre-pit and an R region having apre-groove, exhibiting good recording/reproduction properties meetingDVD specifications in both ROM and R regions.

We have intensely attempted to solve the above problems and have finallyfound that in a DVDR medium requiring forming a high-density recordingpit with a smaller size than a beam spot, the pre-pit and the pre-groovemay have the same depth if their depths are more than λ₂/4 and thatcontrolling half value widths of the pre-pit and the pre-groove andproviding a tilting angle, in particular a tilting angle in a tangentialdirection in the pre-pit, allow a signal to be satisfactorily providedfrom the ROM region. We have also found that a refractive index of a dyematerial used in a recording film can be adjusted to give more favorableproperties, resulting in this invention.

Specifically, this invention provides

1. a recordable optical recording medium comprising a recording layercontaining an organic dye which can absorb a laser beam and a metalreflective layer directly or via another layer on a transparentsupporting substrate having a pre-groove and a pre-pit, wherein theorganic dye has a refractive index nk of 2.2 or more at a reproductionwavelength λ₂; in relation to the reproduction wavelength λ₂, the depthsof the pre-groove and the pre-pit on the substrates are more than λ₂/4;and the following equations are satisfied:

0.25r≦wg≦0.38r:

0.25≦wp/wg≦0.75;

θgr≦θpr; and

 θpr≦θpt

 wherein r is a recording laser beam diameter represented by λ₁/NA whereλ₁ is a recording wavelength [μm] and NA is a numerical aperture for anobject lens; wg [μm] and θgr are a half value width and a cross-sectiontilting angle in a substrate radial direction for the pre-groove,respectively; and wp [μm], θpr and θpt are a half value width, across-section tilting angle in a substrate radial direction and across-section tilting angle in a tangential direction for the pre-pit,respectively;

2. The recordable optical recording medium as described in paragraph 1wherein the pre-groove and the pre-pit formed on the substrate furthersatisfy the relationship of θgr <θpt;

3. The recordable optical recording medium as described in paragraph 1or 2 wherein the pre-groove and the pre-pit have the same depth;

4. The recordable optical recording medium as described in any ofparagraphs 1 to 3 wherein the recording layer containing the organic dyeis formed on the pre-pit and the pre-groove with a film thickness in therange of 50 nm to 150 nm;

5. The optical recording medium as described in any of paragraphs 1 to 4wherein the dye contained in the recording layer is an organic dyecomprising at least one pyrrole unit or a metal complex thereof;

6. The optical recording medium as described in paragraph 5 wherein thedye contained in the recording layer is a pyrromethene-metal complexrepresented by formula (1):

 wherein R1 to R13 independently represent hydrogen, halogen,substituted or unsubstituted C₁-C₁₂ alkyl, substituted or unsubstitutedC₁-C₁₂ alkoxy, and substituted or unsubstituted C₆-C₂₀ aryl; and M is acentral metal;

7. The optical recording medium as described in any of paragraphs 1 to 6wherein λ₁ is 0.63 μm to 0.66 μm and NA is 0.60±0.1;

8. The optical recording medium as described in any of paragraphs 1 to 7having a structure where on a transparent substrate, a recording layer,a reflective layer, an adhesion layer directly or via another layer andanother substrate are laminated.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1(a) shows a cross section of a pre-groove in an R region in aradial direction;

FIG. 1(b) shows a cross section of a pre-pit in an ROM region in aradial direction; and

FIG. 1(c) schematically shows a cross section of the pre-pit in atangential direction.

DESCRIPTION OF THE SYMBOLS

1: a substrate;

2: a pre-groove;

3: a pre-pit;

d: a depth;

wg: a half value width of the pre-groove;

θgr: a cross-sectional tilting angle of the pre-groove in a radialdirection;

wp: a half value width of the pre-pit;

θpr: a cross-sectional tilting angle of the pre-pit in a radialdirection;

θpt: a cross-sectional tilting angle of the pre-pit in a tangentialdirection.

BEST MODE FOR CARRYING OUT THE INVENTION

An optical recording medium according to this invention has a structurewhere a dye-containing recording layer, a reflective layer and aprotective layer are sequentially formed on a substrate having an ROMregion consisting of a pre-pit and an R region consisting of apre-groove, which has the same depth as that of the pre-pit, and furtherhas a structure where a dummy substrate is laminated on the protectivelayer via an adhesive. The pre-pit in the ROM region and the pre-groovein the R region have particular shapes.

The shapes of a pre-pit in the ROM region and a pre-groove in the Rregion will be described with reference to FIG. 1.

Preferably, both pre-groove 2 in the R region and pre-pit 3 in the ROMregion formed in a substrate 1 have a depth (d) in the range of λ₂/4 toλ₂/3 both inclusive where λ₂ is a reproduction wavelength. For example,when a reproduction wavelength for a DVDR is 650 nm, these may bedesirably formed with a depth in the range of 162.5 to 216.7 nm bothinclusive. If the depth is lower then the range, providing a pre-pitsignal amplitude in the ROM region becomes difficult regardless of theirshapes. On the other hand, if the depth is larger than the range,substrate molding become quite difficult and thus it is impractical.

A half value width wg of the pre-groove 2 (a pre-groove width at the ½depth of the pre-groove) in the R region shown in FIG. 1(a) can beoptimized in the wg/r range of 0.25 to 0.38 where r is a beam spot sizedefined as λ₁/NA, depending on the type of the dye contained in therecording layer and a deposition process. For example, when areproduction wavelength λ₁ in a DVDR is 650 nm (0.65 μm) and a numericalaperture NA of an object lens is 0.65, a beam spot size r is about 1 μmand therefore, a half value width of the pre-groove 2 is in the range of0.25 to 0.38 μm. Control of a dependent shape on the pre-groove, i.e., ashape of a reflective layer interface (depth and width) is similarlyimportant. When the pre-groove half value width is less than 0.25,signal leakage (crosstalk) through a land tends to be increased, leadingto signal degradation (e.g., a jitter value). If it is more than 0.38,it may undesirably cause substantial degradation in transferabilityduring molding a substrate.

A pre-pit half value width wp (a pre-pit width at the ½ depth of thepre-pit) in the ROM region shown in FIG. 1(b) may be selected such thatin relation to the pre-groove, wp/wg becomes relatively narrower in therange of 0.25 to 0.75 to particularly provide a signal modulation factorwith a finer pit, which can be easily balanced with a signal in the Rregion. If it is less than 0.25, it may cause extreme reduction in atracking output in the ROM region. If it is larger than 0.75, aninsufficient signal modulation factor may be achieved in the ROM region.With reference to the pre-groove half value width wg as described above,a pre-pit half value width is in the range of 0.0625 to 0.285 μm, but itmay be appropriately selected such that the above depth is consistentwith the below tilting angle.

In this invention, the cross section of the pre-pit is also defined. Inparticular, in terms of a pit cross-section tilting angle in a radialdirection θpr and a pit cross-section tilting angle in a track tangentline direction (tangential direction) θpt (FIG. 1(c)), a substrate inwhich θpr is different from a pre-groove titling angle θgr is preparedfor adjusting balance between the R region and a signal amplitude, sothat a modulation factor may be easily provided when θpr≧θgr.Furthermore, in terms of a tilting angle in a tangential direction inthe pre-pit, signal quality may be improved in the ROM region. Inaddition, the pre-pit may have the same depth as that of the pre-groove.

A cross-section tilting angle θgr of the pre-groove 2 is preferably 45to 65°, more preferably 55 to 65°. A cross-section tilting angle θpr ina substrate radial direction of the pre-pit 3 is preferably 55 to 75°,more preferably 65 to 75° while the above relationship θgr≦θpr issatisfied. A cross-section tilting angle θpt in a tangential directionof the pre-pit 3 is preferably 60 to 80°, more preferably 65 to 80°while the above relationship θpr≦θpt is satisfied.

The shapes of the pre-groove and the pre-pit (width, depth and angle)can be controlled by a shape and an irradiation intensity of anirradiated laser cutting beam during exposure to a beam with a largelaser power covering the entire photoresist film in its thicknessdirection in preparing a stamper template. The angle and the width maybe adjusted to some extent by molding conditions.

The pre-groove and the pre-pit may be wobbled with individuallyoptimized amplitude. In addition, a land pre-pit for address informationmay be separately formed between wobbled pre-grooves (land).

The shapes of the pre-groove and the pre-pit may be determined by STM,AFM or SEM observation of a frozen broken-out section.

In this invention, a substrate may be made of a material which istransparent at a recording/reproduction wavelength λ₂ and exhibits asmaller optical anisotropy. Examples of a material which can be usedinclude polymers such as polycarbonates, polyacrylates,polymethacrylates, polyolefins and epoxy resins; and inorganic materialssuch as glasses. Polycarbonate resins are preferable because theyexhibit good balance between optical transparency and heat resistanceand have good moldability. Polyolefins having a ring structure aresimilarly desirable because of their smaller optical anisotropy andlower hygroscopicity.

A preferable recording layer used in this invention has a refractiveindex nk of 2.2 or more at a reproduction wavelength λ₂ and has a filmthickness of 50 nm to 150 nm over the pre-pit or pre-groove forobtaining an adequate reproduction output from the ROM region whilemaintaining good recording properties in the R region. A refractiveindex less than 2.2 tends not to give a signal amplitude in the ROMregion.

A film thickness of the recording layer beyond the above range led tosignificant deterioration in recording quality.

Specific examples of a dye used herein include macrocyclic aza-annulenedyes such as phthalocyanine dyes, naphthalocyanine dyes and azaporphyrindyes with 1 to 4 meso-nitrogens; porphyrin dyes; azo dyes; indoanilinedyes; azulenium dyes; pyrromethene dyes; and polymethine dyes such ascyanine dyes, melocyanine dyes and squalirium dyes. Among these,preferable dyes exhibiting good durability and good recording propertiesin high-density recording were metal complex dyes comprising at leastone pyrrole unit. Pyrromethene-metal complex dyes represented bychemical formula (1) are particularly preferable as dyes with a higherrefractive index:

wherein R1 to R13 independently represent hydrogen, halogen, substitutedor unsubstituted C₁-C₁₂ alkyl, substituted or unsubstituted C₁-C₁₂alkoxy, and substituted or unsubstituted C₆-C₂₀ aryl; and M is a centralmetal.

Examples of a halogen atom in R1 to R13 include fluorine, chlorine,bromine and iodine atoms. Examples of substituted or unsubstituted alkylinclude methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, t-butyl, n-pentyl, isopentyl, 2-methylbutyl, 1-methylbutyl,neopentyl, 1,2-dimethylpropyl, 1,1-dimethylpropyl, cyclopentyl, n-hexyl,4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl,3,3-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl,2,2-dimethylbutyl, 1,2-dimethylbutyl, 1,1-dimethylbutyl, 2-ethylbutyl,1-ethylbutyl, 1,2,2-trimethylbutyl, 1,1,2-trimethylbutyl,1-ethyl-2-methylpropyl, cyclohexyl, n-heptyl, 2-methylhexyl,3-methylhexyl, 4-methylhexyl, 5-methylhexyl, 2,4-dimethylpentyl,n-octyl, 2-ethylhexyl, 2,5-dimethylhexyl, 2,5,5-trimethylpentyl,2,4-dimethylhexyl, 2,2,4-trimethylpentyl, 3,5,5-trimethylhexyl, n-nonyl,n-decyl, 4-ethyloctyl, 4-ethyl-4,5-dimethylhexyl, n-undecyl, n-dodecyl,methyl-2,4-dimethylheptyl, 2,2,5,5-tetramethylhexyl,1-cyclopentyl-2,2-dimethylpropyl and 1-cyclohexyl-2,2-dimethylpropyl.Examples of substituted or unsubstituted C₆ to C₂₀ aryl include phenyl,nitrophenyl, cyanophenyl, hydroxyphenyl, methylphenyl, dimethylphenyl,trimethylphenyl, ethylphenyl, diethylphenyl, triethylphenyl,n-propylphenyl, di(n-propyl)phenyl, tri(n-propyl)phenyl,isopropylphenyl, di(isopropyl)phenyl, tri(isopropyl)phenyl,n-butylphenyl, di(n-butyl)phenyl, tri(n-butyl)phenyl, isobutylphenyl,di(isobutyl)phenyl, tri(isobutyl)phenyl, sec-butylphenyl,di(sec-butyl)phenyl, tri(sec-butyl)phenyl, t-butylphenyl,di(t-butyl)phenyl, tri(t-butyl)phenyl, dimethyl-t-butylphenyl,fluorophenyl, chlorophenyl, bromophenyl, iodophenyl, methoxyphenyl,ethoxyphenyl, trifluoromethylphenyl, N,N-dimethylaminophenyl, naphthyl,nitronaphthyl, cyanonaphthyl, hydroxynaphthyl, methylnaphthyl,fluoronaphthyl, chloronaphthyl, bromonaphthyl, iodonaphthyl,methoxynaphthyl, trifluoromethylnaphthyl and N,N-dimethylaminonaphthyl.

Any metal capable of forming a complex with a dipyrromethene compoundcan be used as a central metal M without limitations, but the centralmetal is preferably selected from transition metals such as Ni, Co, Cu,Mn, Zn and Pd in the light of stability and optical properties.

Of course, the above dyes can be combined for improving recordingproperties and/or durability, and can be also combined with one or moredyes other than those described above. The recording layer may becomposed of a single layer or two or more layers.

The recording layer containing the above dye may be deposited by anappropriate application method such as spin coating, spray coating androll coating. For application, a solution of the dye in a solvent, whichdoes not affect any damage to a substrate, is prepared, and the solutionis applied and then dried. A solvent is appropriately selected from thegroup consisting of aliphatic or alicyclic hydrocarbons such as hexane,heptane, octane and methylcyclohexane; aromatic hydrocarbons such astoluene and xylenes; ethers such as dibutyl ether and isopropyl ether;alcohols such as ethanol, tetrafluoropropanol and methyl cellosolve; andhalogenated solvents such as chloroform and dichloromethane. Thesesolvents may be used alone or in combination of two or more.

When two or more recording layers are laminated, it is preferable toselect a solvent which gives no damage to a previously-formed layer,e.g., a solvent having different polarity for application of the upperrecording layer.

The recording layer may be formed by vacuum deposition. This method iseffective when the substances to constitute the recording layer have lowsolubility in solvents or when it is impossible to select a solventwhich gives no damage to the substrate used. It is generally preferablebecause it can be controlled to give an even film thickness.

On the recording layer, there is formed a reflective layer made of ametal such as Au, Ag, Pt and Cu or an alloy thereof. Au is particularlypreferable because of its stability to oxygen and moisture. Thereflective layer may be deposited by an appropriate method such as vapordeposition, sputtering and ion plating. The reflective layer has a filmthickness of 10 nm to 200 nm, preferably 50 nm to 150 nm. Anintermediate layer may be formed between the metal reflective layer andthe recording layer for improving interlayer adhesion and a reflectance.

On the reflective layer, a protective layer may be formed, which may bemade of a polymer such as those polymerized by a general radicalreaction (e.g., acrylates and methacrylates) and those polymerized byphoto-induced cation polymerization such as epoxy polymers. These resinsmay be homopolymerized or copolymerized with other monomers and/oroligomers. UV curable resins are desirable. The protective layers may beformed by an appropriate method such as spin coating, screen-printingand bar coating. In the light of practical work, spin coating is oftenused. These films may have a thickness of 1 μm to 100 μm, desirably 1 to20 μm.

This invention will be described with reference to, but not limited to,Examples.

EXAMPLES 1 TO 8 AND COMPARATIVE EXAMPLES 1 TO 8

A 20 g/L solution of one of pyrromethene dyes represented by formulas(A) to (C) in ethylcyclohexane was spin-coated on an injection-moldedpolycarbonate substrate with a thickness of 0.6 mm and a diameter of 120mmφ having a spiral groove with a pitch of 0.74 μm and a pre-pit in apart of a lead-in region on the extension lines of the pre-groove toform a dye layer. On the dye layer was deposited by sputtering an Aureflective layer to 100 nm. Then, on the product was applied a UVcurable resin SD-17 (Dainippon Ink And Chemicals, Inc.) and it was curedby UV. On the resin layer was laminated a polycarbonate substrate with athickness of 0.6 mm as described above via Z8412 (JSR) radical adhesive,to prepare an optical recording medium.

The optical recording medium was evaluated for a signal modulationfactor (I14/I14H) according to DVD specifications for a pre-pit using adisk tester “DDU-1000” (Pulstec Industrial Co., Ltd.) at wavelength: 658nm and NA: 0.60, and for a modulation factor (I14/I14H) and a jitter ina recording region (clock to pit jitter) during recording an EFM signalon the pre-groove.

Table 1 shows the dyes, the pre-pit and the pre-groove shapes in thesubstrate tested in Examples and Comparative Examples and the signalevaluation results, where the pre-groove and the pre-pit shapes in thesubstrate were determined on the basis of AFM and SEM (cross section)observation data.

TABLE 1 Dye film Substrate shape Signal properties Ref. Thick- Indexness d wg wp θgr θpr θpt R region ROM region Dye (%) (nm) (nm) (μm) (μm)wg/r wp/wg (°) (°) (°) jitter Modul. factor Modul. factor Ex. 1 A 2.62100 175 0.35 0.20 0.32 0.57 60 70 72 7.5% 0.68 0.65 Ex. 2 A 2.62 100 1750.35 0.25 0.32 0.71 60 70 72 7.5% 0.68 0.60 Ex. 3 A 2.62 100 175 0.350.25 0.32 0.71 55 68 68 7.9% 0.66 0.60 Ex. 4 A 2.62 100 175 0.38 0.150.35 0.39 60 70 72 7.4% 0.65 0.72 Ex. 5 A 2.62  60 175 0.38 0.15 0.350.39 60 70 72 8.5% 0.60 0.72 Ex. 6 A 2.62 140 190 0.38 0.15 0.35 0.39 6066 68 7.9% 0.75 0.65 Ex. 7 A 2.62 110 190 0.30 0.20 0.28 0.67 61 65 688.5% 0.68 0.66 Ex. 8 B 2.22 110 190 0.30 0.20 0.28 0.67 61 65 68 7.9%0.65 0.61 Comp. 1 A 2.62 100 175 0.35 0.27 0.32 0.77 55 68 68 7.9% 0.660.55 Comp. 2 A 2.62 100 175 0.25 0.20 0.23 0.80 61 65 68 10.1% 0.66 0.68Comp. 3 A 2.62 100 175 0.35 0.20 0.32 0.57 60 50 50 7.5% 0.68 0.55 Comp.4 A 2.62 100 175 0.35 0.20 0.32 0.57 60 60 45 7.5% 0.68 0.50 Comp. 5 A2.62 120 150 0.30 0.20 0.28 0.67 55 60 60 9.5% 0.61 0.55 Comp. 6 C 2.15100 175 0.38 0.15 0.35 0.39 60 70 72 8.1% 0.60 0.55 Comp. 7 C 2.15 100190 0.30 0.20 0.28 0.67 61 65 68 8.9% 0.59 0.53 Comp. 8 A 2.62 100 1750.44 0.20 0.41 0.45 61 65 68 Tracking failure 0.68

INDUSTRIAL APPLICABILITY

According to this invention, by defining the shapes of a pre-groove inan R region and a pre-pit in an ROM region as disclosed herein, apre-pit and pre-groove in an optical recording medium in which both Rand ROM regions satisfy the DVD specifications and which exhibits goodrecording/reproduction properties can be formed in one step from astamper template by, for example, injection molding, allowing massproduction of such media.

What is claimed is:
 1. A recordable optical recording medium comprisinga recording layer containing an organic dye which can absorb a laserbeam and a metal reflective layer directly or via another layer on atransparent supporting substrate having a pre-groove and a pre-pit,wherein the organic dye has a refractive index nk of 2.2 or more at areproduction wavelength λ₂; in relation to the reproduction wavelengthλ₂, the depths of the pre-groove and the pre-pit on the substrates aremore than λ₂/4; and the following equations are satisfied:0.25r≦wg≦0.38r; 0.25≦wp/wg≦0.75; θgr≦θpr; and θpr≦θpt wherein r is arecording laser beam diameter represented by λ₁/NA where λ₁ is arecording wavelength [μm] and NA is a numerical aperture for an objectlens; wg [μm] and θgr are a half value width and a cross-section tiltingangle in a substrate radial direction for the pre-groove, respectively;and wp [μm], θpr and θpt are a half value width, a cross-section tiltingangle in a substrate radial direction and a cross-section tilting anglein a tangential direction for the pre-pit, respectively.
 2. Therecordable optical recording medium as claimed in claim 1 wherein thepre-groove and the pre-pit formed on the substrate further satisfy therelationship of θgr<θpt.
 3. The recordable optical recording medium asclaimed in claim 2 wherein the pre-groove and the pre-pit have the samedepth.
 4. The recordable optical recording medium as claimed in claim 3wherein the recording layer containing the organic dye is formed on thepre-pit and the pre-groove a film thickness in the range of 50 nm to 150nm.
 5. The recordable optical recording medium as claimed in claim 4wherein the dye contained in the recording layer is an organic dyecomprising at least one pyrrole unit or a metal complex thereof.
 6. Therecordable optical recording medium as claimed in claim 5 wherein thedye contained in the recording layer is a pyrromethene-metal complexrepresented by formula (1):

wherein R1 to R13 independently represent hydrogen, halogen, substitutedor unsubstituted C₁-C₁₂ alkyl, substituted or unsubstituted C₁-C₁₂alkoxy, and substituted or unsubstituted C₆-C₂₀ aryl; and M is a centralmetal.
 7. The recordable optical recording medium as claimed in claim 6wherein λ₁ is 0.63 μm to 0.66μm and NA is 0.60±0.1.
 8. The recordableoptical recording medium as claimed in claim 7 having a structure whereon a transparent substrate, a recording layer, a reflective layer, anadhesion layer directly or via another layer and another substrate arelaminated.
 9. The recordable optical recording medium as claimed inclaim 1 wherein the pre-groove and the pre-pit have the same depth. 10.The recordable optical recording medium as claimed in claim 1 whereinthe recording layer containing the organic dye is formed on the pre-pitand the pre-groove a film thickness in the range of 50 nm to 150 nm. 11.The recordable optical recording medium as claimed in claim 1 whereinthe dye contained in the recording layer is an organic dye comprising atleast one pyrrole unit or a metal complex thereof.
 12. The recordableoptical recording medium as claimed in claim 11 wherein the dyecontained in the recording layer is a pyrromethene-metal complexrepresented by formula (1):

wherein R1 to R13 independently represent hydrogen, halogen, substitutedor unsubstituted C₁-C₁₂alkyl, substituted or unsubstituted C₁-C₁₂alkoxy,and substituted or unsubstituted C₆-C₂₀aryl; and M is a central metal.13. The recordable optical recording medium as claimed in claim 1wherein λ₁ is 0.63 μm to 0.66 μm and NA is 0.60±0.1.
 14. The recordableoptical recording medium as claimed in claim 1 having a structure whereon a transparent substrate, a recording layer, a reflective layer, anadhesion layer directly or via another layer and another substrate arelaminated.